Fungus Gnats - can they live on felt?

Hello I feel your pain with the fungus gnats...theyre a true nightmare. What they manage to survive is mind blowing! From my experience they seem to be able to live and thrive in almost anything! In my clones, under the fabric pots, in the crevices of my tent! Anywhere water can lurk they will inhabit. I'm sure the sand will help, but if there's even the smallest crack around the stem base, or the edge of the pot and the sand they'll find a way. And what are the 2 tiny pots in the lefthand corner of your tent? They didn't seem to have sand in the photos... I'd stick with your sand idea, but also buy a product called mosquito bites, its looks like brown rocky sand, it seems to work pretty good, line in in the pots, in the water catchers in the bottom, and grind some up and leave it in water for 24 hours and then water all soil areas with it, it kills larvae and doesnt hurt the roots or plants. Try doing the watering method a few times over a week or two and watch for them to go away. Also check the bottom of your tent and the liner for any possible fluids or spills and do a nice bleach water wipe down.👍 Good luck my friend, keep up the good fight.